Infliximab belongs to the class of medications called biological response modifiers ("biologics") or TNF blockers. It is used in addition to methotrexate, to treat moderate-to-severe rheumatoid arthritis in adults.

Subcutaneous infliximab is also used to maintain remission of symptoms of moderately-to-severely active ulcerative colitis or Crohn’s disease that has not responded to other treatment options. In these cases, it is used after intravenous infliximab treatment has been completed to maintain its effects.

People with rheumatoid arthritis, ulcerative colitis, and Crohn’s disease produce extra amounts of a protein called tumour necrosis factor (TNF), which causes pain, inflammation, and damage. Infliximab blocks the production of TNF and decreases the inflammation in the joints and on the skin.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

When treating rheumatoid arthritis, the usual starting dose of infliximab is 120 mg injected subcutaneously (under the skin), once a week for 5 weeks. After the first 5 doses, the recommended dose is 120 mg injected subcutaneously once every 2 weeks. It is usually injected in the front of the thigh or abdomen.

If you are starting infliximab as an intravenous (into a vein) infusion, your doctor will recommend a different series of starting doses.

Treatment of Crohn’s disease and ulcerative colitis is started with intravenous doses of infliximab, referred to as induction. After induction, the regular dose of infliximab is 120 mg injected subcutaneously once every 2 weeks, starting 4 weeks after the last induction dose.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.

Infliximab is used with the guidance and supervision of a doctor. Your doctor or nurse will help you with preparing and injecting your first dose (or first few doses). Do not attempt to prepare or inject this medication on your own until you completely understand how to inject a dose. If you are having difficulty giving yourself injections, talk to your health care provider.

If you miss a dose and it is 7 days or less since the missed dose, take it as soon as possible and continue with your regular dosing schedule. If it is 8 days or more since the missed dose, skip the missed dose and continue with your regular dosing schedule.

This medication must be refrigerated at 2°C to 8°C (do not freeze it) and kept out of the reach of children. Do not freeze or shake. Remove the medication from the refrigerator 30 minutes before administering the injection. This will allow it to warm to room temperature before injecting. This medication may be also stored at room temperature for up to 28 days.

Each prefilled pen containing a sterile clear-to-opalescent, colourless-to-pale-brown solution, contains 120 mg of infliximab. Nonmedicinal ingredients: acetic acid, sodium acetate trihydrate, sorbitol, polysorbate 80, and water for injection.

You should not use infliximab if you:

• are allergic to infliximab, mouse proteins, or any ingredients of the medication
• have moderate-to-severe congestive heart failure
• have or are at risk of severe infections such as sepsis, abscesses, tuberculosis, or opportunistic infections (infections that strike people with weakened immune systems)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal pain
• back pain
• cough
• diarrhea
• dizziness
• fatigue
• generalized pain
• headache
• itchiness
• reactions at the injection site (e.g., pain, itching, redness, swelling, bruising, bleeding, cold or tingling sensation)
• upset stomach

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• new or worsening shortness of breath
• signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of heart problems (e.g., fast, irregular heartbeat or pulse, chest pain, sudden weight gain, difficulty breathing, leg swelling)
• signs of nervous system problems (e.g., vision changes, weakness in arms, legs or numbness or tingling in any part of the body)
• skin problems (e.g., red, itchy rash, peeling or blistering skin, reddish-purple skin rash, thread-like white-grey lines in the inner part of the mouth)
• sores, warts, or bumps on the skin that do not heal
• symptoms of an infection (e.g., fever, chills, pain, swelling, or pus)
• symptoms of liver damage (e.g., yellow skin or eyes, dark urine, loss of appetite, abdominal pain, fever, and fatigue)
• symptoms of lupus (e.g., chest discomfort/pain, shortness of breath, joint pain, rash on the cheeks or arms)
• symptoms of lymphoma (e.g., unusual fatigue, weakness, night sweats, swollen lymph nodes)
• symptoms of upper respiratory infections (e.g., sore throat, fever, cough, fatigue, chest congestion)
• symptoms of a urinary tract infection (e.g., pain when urinating, urinating more often than usual, low back or flank pain)

Seek immediate medical attention if any of the following occur:

• seizures
• symptoms of an allergic reaction (such as difficulty breathing, hives, swelling of the face or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergic reactions: In rare cases, some people may develop an allergic reaction to this medication. Signs of an allergic reaction include a severe rash, hives, swollen face or throat, or difficulty breathing. If these occur, contact your doctor immediately.

Blood disorders: Rarely, people taking this medication have become deficient in certain types of blood cells. This may lead to problems with blood clotting, the immune system, or the transport of oxygen through the body. Contact your doctor immediately if you develop a fever, easy bruising, paleness, or bleeding while taking this medication.

Cancer: Compared to the general population, people taking infliximab have a slightly greater risk of developing a cancer of the immune system (known as lymphoma). However, the risk of developing this type of cancer is still rare.

In general, people with severe rheumatoid arthritis who take medications that suppress the immune system over long periods of time may also have a higher risk of developing lymphoma, even if they don't take infliximab. Contact your doctor if you develop symptoms of lymphoma (such as fatigue, weight loss, fever, swollen glands, night sweats, and itching). (Note though that these may also be symptoms of other conditions.)

Other forms of cancer, such as cervical and certain skin cancers, have also been seen in people who are taking infliximab. Talk to your doctor about the risks and benefits of using this medication.

Drowsiness/dizziness: Infliximab can cause drowsiness or dizziness, affecting your ability to drive or operate machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how you are affected by this medication.

Heart failure: This medication may cause symptoms of congestive heart failure to become worse. If you have mild heart failure you should be closely monitored by your doctor while taking this medication. If you notice symptoms of congestive heart failure (such as swelling of the hands or feet and difficulty breathing), contact your doctor immediately. People with moderate or severe congestive heart failure should not take infliximab.

Hepatitis B: People infected with hepatitis B (an infection that can damage the liver) may have a relapse of their condition while taking this medication. If you are at risk for hepatitis B, your doctor may want to test you for this infection before starting treatment with infliximab and will follow your condition closely while you are taking the medication. If you notice symptoms of a liver problem (see below), contact your doctor immediately.

Immune system disorders: Some people who take this medication have developed lupus-like syndrome, an autoimmune disease (a condition where the body is attacked by its own immune system). Symptoms of lupus-like syndrome include chest pain, joint pain, difficulty breathing, and a skin rash (usually on the cheeks and arms) that is sensitive to the sun. If you develop these symptoms, contact your doctor as soon as possible.

Infections: This medication can increase the risk of developing an infection, including serious infections such as sepsis, pneumonia, and tuberculosis. Before starting infliximab treatment, your doctor may test to see if you have tuberculosis. If you notice signs of an infection such as fever, chills, pain, swelling, coughing or pus, contact your doctor as soon as possible. This medication should also not be started while you have an active infection.

Tell your doctor if you have a history of infections that keep coming back, or other conditions that might increase your risk of infections (e.g., diabetes) or have visited or lived in areas where there is a greater risk of certain kinds of fungal infection (e.g., blastomycosis). While you are taking infliximab, your doctor will monitor you for signs of infection.

Liver problems: Very rarely, people taking infliximab may experience liver problems. Symptoms of liver problems include abdominal pain, dark urine, fatigue, loss of appetite, and yellow eyes or skin. If you notice these symptoms, contact your doctor immediately.

Nervous system disorders: Rarely, this medication may increase the risk of problems with the nervous system or cause existing problems to get worse. If you experience confusion, seizures, vision changes, tingling or numbness, or weakness in your arms or legs while taking this medication, contact your doctor immediately.

Vaccines: Live vaccines such as yellow fever, BCG, cholera, typhoid, varicella, meningococcal, and diphtheria should not be given while you are receiving infliximab. They work by administering a small amount of live bacterium into the body to cause the body to develop defenses against them. When they are given at the same time as a medication that may reduce the strength of your immune system, it may cause a severe infection.

Other vaccines given when you are receiving this medication may not work well enough to protect you from infections. Talk to your doctor about which vaccinations you need before starting treatment.

Pregnancy: This medication is not recommended for use during pregnancy as it crosses the placenta and the effects on the developing baby are not known. Infants born to those who used this medication during pregnancy appear more likely to experience severe and possibly life-threatening infections. Anyone who may become pregnant should use an effective method of birth control while they are taking this medication and for at least 6 months after the last treatment.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and taking infliximab, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of this medication have not been established for children.

Seniors: Seniors may be at an increased risk of severe infections with this medication.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.